Telegraph switching system



April 20, 1926. 1,581,844

C. E. LOMAX TELEGRAPH SWITCHING SYSTEM Filed Feb. 1, 1922 T'LUEH DIElarenma Elmmax Patented Apr. 20,

UNITED STATES PATENT OFFICE.

CLARENCE LOMAX, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE' ASSIGNMENTS,TO AUTOMATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION OF DELA-WARE.

TELEGRAPH SWITCHING SYSTEM.

Application filed February 1, 1922. Serial No. 533,362.

To all whom it may concern:

Be it known that I, CLARENCE E. LoMAx, a citizen of the United States ofAmerica, and a resident of Chicago, Cook County, and State of Illinois,hayeiiivented certain new and useful Improvements in Telegraph SwitchingSystems, of which the following is a specification.

The present invention relates in general to telegraph switching systems,and more specially to systems of this character comprising a pluralityof telegraph stations eaph having a line extending to a centralexchange. or switching-point, together with suitable automatic switchingdevices at the exchange for connecting any calling telegraph line withany desired called telegraph line. A system of this kind is useful inbanks or other business establishments as a means of communicatingbetween the different departments, and in case telegraph apparatus'oithe printing type is used, as is contemplated, the system is especiallyuseful in that it prescrvcsa record of all communications.

.While ordinarily there would be no particular difiiculty in providingmeans for switching one line of a plurality of lines in connection withany of the other lines, in

the .case of telegraph lines, the problem is complicated by thefa'ctthat such lines are norn'ially operated on, closed circuit, andspecial arrangements have to be provided for establishing theinterstation circuits at the same time that the local circuits of thestations involved are broken, in order to avoid opening the circult atany station during the switching process.

The particular arrangement provided for this purpose by the presentinvention will now be described and its operation will be explained inreference to the accompanying drawings, which shows diagrammatically theapparatus and circuits involved in set ting up a connection between thetelegraph station A and the telegraph station B.

Although as previouslyindicated it is intended to use the invention inconnection with printing telegraph-equipment, such aparatus 1s exceedinl com licated and since the invention has to do merely with theestablishment of theinterstation circuits, it has not been considerednecessaryto show complete station equipment of this'compli- 1,279,352,issued Sept. 18, 19 18, which isused for. controlling the automaticswitch associated with this station at 'the exchange. The key K isprovided for closing the circuit of the calling device. The lamp L is abusy lamp, and is lighted whenever it is attempted to establishconnection with a busy station.

The line conductors 2, 3, 4c and 5 extend to the central-exchange orswitching point and terminate in the individual connector switch H,which is preferably of the. mechanical construction shown and describedin the patent to Keith, Erickson & Erickson, No. 815,176, granted March13, 1906. As will be understood this switch may have access to onehundred lines which terminate in contact sets arranged in a plurality ofhorizontal rows or levels. In order to connect with a desired line, theswitch is first operated to raise its wipers vertically to a positionoppo-,

site the particular row or level in which the desired line appears, andis then operated to rotate its wipers into connection with the desiredline. In thecase of the connector H, these operations of the connectorare all controlled by the subscriber at station A by means of thecalling device CD, as will appear more clearly hereinafter.

There may be one hundred stations in the system illustrated, and eachstation is provided with a connector switch exactly like the connectorH. Each connector has access to all of the lines in the system, and thusthe party at any station, by suitably operatinghis individual] connectorswitch, can establish a connection with any other station. i

It may be that under some circumstances a number of the stations will belocated in the same department, and of such a character that it is amatter of indilference to a calling subscriber as to which of theparticular stations in such department he 0btains connection with.Certain arrange- Ski ments shown herein are arranged to take careof thissituation by providing for automatic trunk selection by the connectorswitches in the case of station lines which may be arrangedin groupsunder the circumstances mentioned. subscriber,.in calling a departmenthaving a number of grouped stations, will call the number of thedepartment, and will automatically establish connection with a lineleading to the first idle station in such department.

Having pointed out the general features of the invention, its operationwill now be described more in detail, and for this purpose it will beassumed that the party at station A desires to establish a connectionwith the party at station B. Before proceeding, it will be well to pointout that the telegraph apparatus at the station A is included in aclosed circuit which extends from round at G by way of resistance a,restmg contact of armature 60 and the said armature, conductor 1, switchS, magnet M, conductor 2, normally closed contact springs controlled byarmature 76, and resistance 1 to the grounded battery B. It will be.seen also, that the telegraph apparatus at station B is included in aclosed circuit similar to the one described for station A, except thatit includes the battery B In practice,

the batteries B and B will be the same ordifi'erent batteries dependingon the distance between the stations and perhaps on other circumstances.The telegraph battery, or batteries, are preferably ofhigh voltage, asis inost suitable for telegraph systems. The other batterysymbols shownin the drawinglall refer to the same battery, which is the one used forsupplying current to the automatic switchesat the exchange.

Now, since the two stations are normally. connected in alocal closedcircuit, the establishment of a connection between the two stations willnecessarily involve the opening of both local circuits and thecompletion of an interstation circuit in which the telegraph equipmentat both stationsis connected in series. While the inter-station circuitmight conceivably include both batteries, in case different batterieswere employed at the two stations, according to the present arrangementonly one battery is used in each connection, and the battery used is theone at the called station.

To extend a connection, the key K isfirst operated in order to, connectup the, calling device CD after which the calling device is operated. inaccordance, with the two digits in the number assigned to the calledstation, which may be assumed to be the number 55. When the key K isoperated, a circuit is completed over conductor 5- for the line relay 16of the individual switch H, and the said relay energizes and com: pletesa circuit at armature 61 for the slowacting release relay 17. Uponenergizing, the latter relay disconnects relay 15 at arni ature 62 andatthe saine point connects ground to the conductor 6, whereby a testpotential is placed on the test contacts 10 and 11 and multiples thereofin banks of the other connector switches. In addition to the foregoing,relay 17 prepares a circuit for the vertical magnet 2% at armature 63.The calling device is now operated in accordance with the first digit.Five interruptions are accordingly produced in the circuit of theline-relay 16, which deenergizes five'ti'mes and transmits a like numberof impulses to the vertical magnet 24 over the following path: Fromground by way of armature 61 and its resting contact, resting contact ofarmature and the said armature, armature 63 and its working contact,shaft controlled off-normal springs 27 and 29, winding of theslow-acting series relay 18', and the winding of the vertical magnet- 24to battery. In response to impulses received over the above circuit thevertical magnet 21 operates to raise the switch shaft step by step untilthe wipers 35,36 and 37 stand "opposite the fifth horizontal level ofbank contacts. series with the vertical magnet and being slow-acting,remains in operated position during the vertical stepping movement. At

its armature '64, relay 18 maintains the impulsing circuit closedthrough its own winding and the vertical magnet, notwithstanding theshifting of the shaft controlled olfnormal springs, which takes place atthe first vertical step of the switch. At the end of the verticalmovement, relay 18. falls back and transfers the impulsing circuit fromthe vertical magnet to the rotary magnet 25.

When the calling device is operated in accordance with the second digitof the number, five more interruptlons are produced in the line circuitand the line relay 16 is deenergized fiye times asbefore. This time,however, the line relay transmits impulses to the rotary magnet 25 overthe" following, path: Fromground'by way of armature 61 and its restingcontact, resting contact of armature'75 and the said armature, armature6 3 and its working contact, off-normal springs 27 and 28 armature 6 1and its resting contact, resting contact of armature 67 and the saidarmature, winding of the slow acting series relay 20', and the windingof the rotary magnet 25 to battery. By the operation of the rotarymagnet, the wipers 35, 36 and 37 are rotated step by step and arefinally broughtto rest in engagement with the particular set of bankcontacts in which the line of station B is terminated, designated in thedrawing by reference characters .38, 39 and 40. Relay20 is energizedinseries with the rotary magnet and Relay 18 is energized in beingslow-acting, remains in operated posi tion during-the rotation of the.switch. At armature 7 0, relay 20 closes a circuit for the sloweactingrelay 22, which is thus also maintained energized .during the rotarymovement of the switch.- At armature 77,

relay 22 disconnects the test wiper 36 from the winding of the switchingrelay 21 and connects it by way of armature 73 andits resting contact tothe winding of'th'e test relay 19. It is noted, that since the testrelay is connected up at the beginning'ot the rotary movement, means isprovided on the series relay 20, consisting. of armature I contact .39,itwill find a ground potential and the test relay 19 will be energized.-The rotary movement having been completed, re-

lays 20 and 22 now fall back, and a locking circuit is completed for theenergized test relay as follows: From the groundedconductor 6 by wa-y ofarmature 66 and its Working contact, normally closed contact springscontrolled byarmature 77 of relay 22, armature 73 and its restingcontact, and the winding of test relay 19 to battery. In its energizedposition the, test relay opens the rotary magnet circuit at armature'67,breaks the circuit to the lower winding of the switchingrelay 21 atarmature 66, and at armature 68- connects conductor 3 to the exchangebattery, thus lighting the lamp L at station A. Since this indicates tothe calling party that the desired station is busy, he will release theconnection by're storing key K It may be assumed, however, that stationB is idle when called. Under these circumstances, when the test wiper 36comes into engagement with test contact 39, it will find no groundpotentials and the test relay 19 will not be energized. Accordingly,when relays 20 and 22 fall back at the end of the rotary movement, acircuit will be established for the switching relay 21 as follows: Fromthe grounded conductor 6 by way of armature 66 and its resting contact,lowerwinding of relay 21, resting contact of armature W and the saidarmature, test wiper 36, test contact 39, conductor 6', armature 62 andthe winding of relay 15 to battery Relays 21 and 15 are energized inseries over the above circuit, and the latter relay disconnectsconductor 4 from ground at armature The switching relay 21, L \onenergizing, establishes a locking circuit 1. r itself at armature 72,opens the circuit f the test relay 19 at armature 7 3,-opens theoperating circuit at armature 75, and at arplished b mature 7 4 connectsdirect ground to the test wiper 36. In addition to the foregoing, at

armature 76 relay 21 disconnects the line conductor 2 of station A fromthe battery B and connects it instead to wiper-37, this operation takingplace simultaneously with the operation of armature 60 by relay 15 whichwas previously described. Both of the local telegraph circuits have nowbeen broken and an inter-station circuit has been established which maybe traced as follows: From ground at G by way of resistance 1",

resting contact of armature 60 and the said armature, conductor 4,switch S, magnet M, conductor 2, working contact of armature 76 and thesaid armature, wiper 37, contact 40, conductor 4, switch S magnet M,conductor 2, nonnally closed contacts controlled by armature 76 of relay21, and'the resistance r to the grounded battery B The establishment ofthe above circuit completes the operations incident to securing thedesired connection.

The two stations being now in communication with each other, the partyat station A may open the switch S, and by suitably manipulating key Kcan transmit code sig nals to the party at station B, which are thererendered audible by means of the sounder magnet M; or, 1n case printingtelegraph apparatus is used at the two stations, the party at station Awill spell out the message he desires to transmit on the keyboard at hisstation, whereupon the message will be printed out on tapes at bothstations simultaneously. It will be understood, of course, that when theautomatic printing equipment is used, the transmission of a message doesnot require the presence of the receiving-operator at the other end, themessage which is sent being printed on-tape as stated, where it isaccessible to the operator or other party at the receiving station whenhe returns.

The release of. the connection is accomrestoring key K as previouslymentione The restoration of this key breaks the circuit ofline relay 16,which falls back and permanently opens the circuit of slow-actingrelease relay 17. The

latter relay upon deenergizing, takes ground oft from conductor 6 inorder to clear the line of'station A for incoming calls, and

wiper 36, thus permitting the deenergization oflelay 15 in the switchassociated with ion now in normal condition, ready for other the calledstation B. All the apparatus is calls. v

The automatic trunk selecting feature of connector H will now bebrieflyexplained. The connectors are preferably provided with extra banks oftest contacts, such as the test contacts 10 and 38, associatedrespectively with stations A and B. The extra test contacts which areassociated with all single or individual stations, are left dead ordisconnected, asshown in the case of the test contact 38 which isassociated with the line of station E. In the case of grouped stationshowever, which are selected auto matically responsive to the calling ofthe group number, whichit may be stated, is the number of thefirststation in the group, each extra test contact is connected'to its'associated regular test contact. This is true of the test contactsassociated with all the stations inthe group except the onesassociatechwith the last station in the group,

' which are left separate or disconnected from each other. The manner inwhich the testcontacts of a grouped line areconnected, is shown in the.case of contacts 10 and 11 associated with the line of station A. Y

Assuming now, that the connector H is operated to establish connectionwith a set of contacts in which is terminated a line extending to thefirst station of a group. If

this station is-busy, the test contact engaged by test wiper 36 willfind a ground potential and'the'test re'lay 19 will be energized, aspreviously explained. At the end of the rotary movement relay 20 willfall back and open thecircuit of relay 22, but the latter relay beingslow-actim will not decnergize immediately. \Vhen re ay 20 falls back acircuit is completed for the'stepping relay 23 as follows: Fromthe-grounded test contact engaged by test wiper 35, (this test contactis permanently connected to the test contact engaged by test wiper 36),by way of test wiper 35, resting contact of armature 69 and the saidarmature, working contact of armature 6 5 and the said armature,interruper contact of rotary magnet 25, and the winding of steppingrelay 23 tobattery. Relay 23 is energized over 'the above circuit, andlocks itself at armature 7 9, at the same time closing acircuit for therotary 'magnet'25 at ari na'ture Relay 20 being now deenergized, theslow-acting relay 22 is energized in parallel with the rotary magnet,andisthus prevented'from' deenergizing. The operation of the rotarymagnet advances the switch wipers into en.-' ga'gement with the next setof bank contacts, The rotary magnet also breaks the .circuit of thestepping relay 23, which accordingly falls back and breaks the rotarymagnet circuit, which then deencrgizes also and again ,closes'itsinterrupter contact.

If the next set or contacts is engagcu also, the foregolng operationswill be repeated,

and it will be understood accordingly, that idle Ifidle, neither testwiper will find a ground and communication with the selected calledstation will be established by theenergi'zation of switching relay 21,as previously pointed out, but if busy, the test contact 36 will findground potential, and the test. relay 19 will'be locked up to light thebusy lamp at the calling station.

It will be seen from the foregoing, that suitable switching-apparatus isprovided, whereby closed circuit telegraph stations, such as stations AandB for example, may be connected in a series circuitwithout-interrupting the flow of current through the instruments at thetwo stations during the process of establishing the connection. This is,of course, accomplished by theenergization, in the case of the stationsmentioned, of the switching relay 21 o't the connector H at the sametime or slightly before. the energization of relay 15 in the connectorassociated with the called station. In order to insure the correcttimingof thcsc relays, relay 15 is provided with a slug of copper, asindicated in the drawing, which renders it slightly slow to'pull up.Resistances such.

ion

as r to 1", inclusive, are provided toprevent short-circuiting of thebatteries or the telegraphfinstruments during the establishment andrelease of. inter-station circuits. The arrangement shown and describedis-intended for use in connection with that type of equipment inwhiclrit is positively required that the flow of current must bemaintained through the telegraph instruments at all times, except duringthe actual transmission of code signals. jCertai-n types of telegraphequipment,- howe'ver, have less rigid require- -ments and permit themomentary breaking of the instrument circuits, preliminary to thetransmission of redeption of a' message; or, the system may -loe'ojf thetype in which a momentary/opening of the circuit is .re quired to beintroduced in order toprepare the equipment tor .thetransmission or reception of messages.- In such cases-the resistanc-es 7" to rt,inclusive, may be omitted,

and ordinary make and break spring combinations maybe used at theconnectors in place ofthe make before break spring combinations whichare shown at armature 76 oi; the connector H and-at armature 7 6 of theconnector associated with station B.

considered to be new will be Having described the invention what ispointed out in the appended claims.

lVhat I claim is:

1. In a telegraph switching system, a plurality of closed local circuittelegraph stations, there being three or more of said stations,automaticfsw'itches for connecting any two stations in series, and relaymeans in said switches for establishing a series circuit between any twoconnectedstations before opening the local-circuits of said stations.

2. In a telegraph switching system, a plurality of closed local circuittelegraph stations, there being three or more of said stations,automatic switches for connecting any two stations in series, saidswitches being individual to said stations and controlled therefrom, andrelay meansin said switches for completing the series circuit betweenany two connected stations before the local circuits are broken.

3. In a telegraph switching system, calling and called stations, closedlocal circuit telegraph instruments at each station, an automatic stepby step switch directly controlled from the calling station to establisha circuit including the instruments at .both

stations in series, and relay means in said 'included in the closedlocal circuit at each station, and an automatic selectively movableswitch directively controlled from the calling station to establishaseries circuit including the instruments at both stations and only oneof-said batteries.

5. In a telegraph switching system, calling and called stations, closedcircuit telegraph instruments at each station, a battery included in theclosed local circuit at each station, an automatic selectively movableswitch directly controlled from the calling station to establish aseries'circuit including the instruments at both stations and the battery at the called station, and means for switching the battery at thecalling station out of circuit.

6. In a telegraph switching system, a plurality of telegraph] stations,telegraphic sending and receiving equipment at each sta tion, automaticselectively movable switching mechanism controlled from any callingstation to connect the sending equipment thereat with the receivingequipment at any called station to establish communication between saidstations said switching mechanism being nonresponsive to said telegraphsending equipment, and an operator controlled variable impulse sender ateach station for controlling said switching mechanism as set forth.

7. In a telegraph switching system, calling and called stations, closedcircuit telegraph instruments at each station, separate 7 battery andground connections in each local circuit, an automatic selectivelymovable switchcontrolled' from the calling station to establish a seriescircuit including the in: struments at both stations, the groundconnection at one station, and the battery connection at the otherstation, and means for automatically opening the other ground andbattery connections when the series circuit is established.

8. In a telegraph switching system, calling and called stations, closedlocal circuit telegraph instruments at eachstation, a battery includedin the closed local circuit at each station, an automatic selectivelymovable switch directively controlled from the calling station toestablish a connection between said stations, and relay means in saidswitch effective upon said connection being established for completing aseries circuit including the instruments'at both stations and only oneof said batteries.

9. In a telegraph switching system, a plurality of stations, telegraphinstruments at each of said stations normally in a closed local circuitinvolving separate ground and battery connections, an automatic switchindividual to each of said stations and directively controlled therefromfor extending a connection to a called station, and relay means in saidswitchesv for automatically completing a series circuit including thein- I struments at both stations and only one battery.

10. In a telegraph switching system, call- 'ing and called stations,closed local circuit battery and a ground connection included in theclosedlocal circuit at each station, an automatic selectively movableswitch directively controlled from the calling station-t0 establish aseries circuit including the instruments at both stations and thebattery at the called station, and means for switching the battery ofthe calling station and the ground at the called station out of circuit.

11. In a telegraph switching system, callingand called stations, closedlocalv circuit telegraph instruments at each station, a bat' tery and agroundcon nection included in the closed local circuit at each station,an automatic selectively movable switch controlled from a callingstation to establish a-series circuit including the instruments at bothstations and the battery at the called station, and automatic means insaid switch eiiective after said series circuit has been completed, forswitching the battery at the calling station and the ground at thecalled station 013i of circuit.

12. Ina telegraph switching system, call- 3 ing and called stations,closed local circuit telegraph instruments at each station, a bat-.

tery included in the closed local circuit at each station, an automaticselectively movable switch directively controlled from the callingstation, to establish-a series circuit including the instruments at bothstations and only one of said batteries, and relay means in said-switchfor establishing said series circuit without, at any time, dlsturb- 10ing the current fiow over said instruments.

In Witness whereof, I hereunto subscribe my name-this 23rd day ofDecember, A. D., 1921.

CLARENCE E. LOMAX.

